In a typical construction of an aircraft wing, a rib box is formed in an interior of the wing. The rib box extends along the longitudinal length of the wing between an inboard end of the wing and an opposite outboard end of the wing. The rib box is positioned laterally between a forward or leading edge of the wing and a rearward or trailing edge of the wing.
The rib box contains a plurality of ribs that extend laterally between a forward spar of the rib box and a rearward spar of the rib box. The plurality of ribs are longitudinally, spatially arranged along the longitudinal length of the wing box. The wing box construction also includes pluralities of stringers that extend longitudinally across the top and bottom of the wing box. The stringers are elongate, narrow reinforcing members that extend along the longitudinal length of the wing box and are secured to the ribs in reinforcing the wing box. The stringers are also connected to the top exterior skin panel of the wing and the bottom exterior skin panel of the wing.
Because the typical aircraft wing tapers as it extends from its inboard end to its outboard end, the interior volume of the wing box decreases as the wing box extends from its inboard end to its outboard end. With the interior volume of the wing box decreasing as the wing box extends from its inboard end to its outboard end, there is decreasing space in the wing box between the front spar and rear spar of the wing box for the stringers. This requires that, at some point along the longitudinal length of the wing box, each stringer must either run out or terminate, or transition from a first cross-sectional area of the stringer to a second cross-sectional area of the stringer, where the second cross-sectional area is smaller than the first cross-sectional area. This typically requires a first stringer having the first cross-sectional area terminating and then beginning again as the second stringer with the second cross-sectional area. The first stringer is connected end to end with the second stringer.
When a stringer transitions from a larger, first cross-sectional area stringer to a smaller, second cross-sectional area stringer, it is necessary that the first stringer and the second stringer be connected end to end. This connection is typically provided by plate fittings that are connected between the opposing ends of the first stringer and the second stringer. For example, where the first stringer and the second stringer have “I” configurations, a plate fitting is attached between the webs of the opposing ends of the first stringer and second stringer, and plate fittings are attached between the top flange and bottom flange of the opposing ends of the first stringer and second stringer. The material typically used to construct the plate fittings is titanium. The titanium plate fittings are attached between the opposing ends of the first stringer and the second stringer by pluralities of fasteners.
The use of the titanium plate fittings and the pluralities of fasteners to connect opposing ends of a first stringer and a second stringer add substantially to the construction time of the wing box. Additionally, the use of the titanium plate fittings and the fasteners to connect opposing ends of a first stringer and a second stringer adds substantially to the weight of the wing box. The use of the titanium plate fittings and the fasteners also adds substantially to the cost of constructing the wing box.